[ih] Arpanet line speed

[Andrew G. Malis]

Noel,

They were digital DS0s. I’m sure that they were less expensive than analog
(although I have no particular documentation of that), and most probably
more reliable as well. As I recall, with the digital circuits, the most
common cause of line outage was microwave fade.

Cheers,
Andy


On Wed, Jan 18, 2017 at 1:32 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>
wrote:

>     > From: "Andrew G. Malis"
>
>     > By the time I came on board in '79, almost all of the links were 56
>     > Kbps ... The 50 Kbps links had been replaced by that point.
>
> Hmmm. I'm trying to remember when the giant rack that contained the 303
> modems at MIT went away. (I should remember this, as I wound up caring for
> the MIT IMPs, but I just don't recall.) Do you know any details of how the
> 56Kbps links worked? I.e. was there a analog modem involved, or was it
> somehow provided by an underlying digital (TDMA of some sort) link, and
> what
> kind of line was it?
>
> Do you know why the change was made? I'm going to guess that possibly it
> was
> cost, that whatever was used for the 56kbps was cheaper than the leased
> lines
> used with the 303s?
>
>         Noel
>
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